Snoring and arousals in full-night polysomnographic studies from sleep apnea-hypopnea syndrome patients

SAHS (Sleep Apnea-Hypopnea Syndrome) is recognized to be a serious disorder with high prevalence in the population. The main clinical triad for SAHS is made up of 3 symptoms: apneas and hypopneas, chronic snoring and excessive daytime sleepiness (EDS). The gold standard for diagnosing SAHS is an overnight polysomnographic study performed at the hospital, a laborious, expensive and time-consuming procedure in which multiple biosignals are recorded. In this thesis we offer improvements to the current approaches to diagnosis and assessment of patients with SAHS. We demonstrate that snoring and arousals, while recognized key markers of SAHS, should be fully appreciated as essential tools for SAHS diagnosis. With respect to snoring analysis (applied to a 34 subjects¿ database with a total of 74439 snores), as an alternative to acoustic analysis, we have used less complex approaches mostly based on time domain parameters. We concluded that key information on SAHS severity can be extracted from the analysis of the time interval between successive snores. For that, we built a new methodology which consists on applying an adaptive threshold to the whole night sequence of time intervals between successive snores. This threshold enables to identify regular and non-regular snores. Finally, we were able to correlate the variability of time interval between successive snores in short 15 minute segments and throughout the whole night with the subject¿s SAHS severity. Severe SAHS subjects show a shorter time interval between regular snores (p=0.0036, AHI cp(cut-point): 30h-1) and less dispersion on the time interval features during all sleep. Conversely, lower intra-segment variability (p=0.006, AHI cp: 30h-1) is seen for less severe SAHS subjects. Also, we have shown successful in classifying the subjects according to their SAHS severity using the features derived from the time interval between regular snores. Classification accuracy values of 88.2% (with 90% sensitivity, 75% specificity) and 94.1% (with 94.4% sensitivity, 93.8% specificity) for AHI cut-points of severity of 5 and 30h-1, respectively. In what concerns the arousal study, our work is focused on respiratory and spontaneous arousals (45 subjects with a total of 2018 respiratory and 2001 spontaneous arousals). Current beliefs suggest that the former are the main cause for sleep fragmentation. Accordingly, sleep clinicians assign an important role to respiratory arousals when providing a final diagnosis on SAHS. Provided that the two types of arousals are triggered by different mechanisms we hypothesized that there might exist differences between their EEG content. After characterizing our arousal database through spectral analysis, results showed that the content of respiratory arousals on a mild SAHS subject is similar to that of a severe one (p>>0.05). Similar results were obtained for spontaneous arousals. Our findings also revealed that no differences are observed between the features of these two kinds of arousals on a same subject (r=0.8, p<0.01 and concordance with Bland-Altman analysis). As a result, we verified that each subject has almost like a fingerprint or signature for his arousals¿ content and is similar for both types of arousals. In addition, this signature has no correlation with SAHS severity and this is confirmed for the three EEG tracings (C3A2, C4A1 and O1A2). Although the trigger mechanisms of the two arousals are known to be different, our results showed that the brain response is fairly the same for both of them. The impact that respiratory arousals have in the sleep of SAHS patients is unquestionable but our findings suggest that the impact of spontaneous arousals should not be underestimated

Upper airway resistance syndrome: evaluation of patients with excessive day time sleepiness non-invasively

Background: Upper airway resistance syndrome (UARS) is a recent concept introduced among sleep disordered breathing (chronic snoring and Obstructive sleep apnea) disorders. UARS also presents with excessive daytime sleepiness (EDS), which is associated with impaired social functioning, work performance and driving ability. However, UARS is not merely a continuum between chronic snoring and obstructive sleep apnea (OSA). Not only UARS patients have equal gender distribution and thin body habitus but they also do not fulfil Polysomnographic criteria of OSA. UARS diagnosis requires oesophageal manometry for diagnosing increased respiratory efforts against increased upper airway resistance (without complete cessation of airflow or hypoxia) and correlating it with EEG arousals to mark an event. Oesophageal manometry is invasive and uncomfortable, therefore, non-invasive means are desirable for evaluation of UARS. The aim of the study is to evaluate the patients with EDS for UARS non-invasively.Methods: 25 consecutive patients with EDS (Epworth Sleepiness Score >9) visiting sleep clinic at a tertiary level hospital in North India were enrolled after informed consent. It was a non-blinded, interventional trial. All enrolled patients underwent nocturnal polysomnography using VIASYS healthcare sleep screen apnea screen cardio polysomnography machine. After PSG, those patients satisfying criteria for OSA were not analysed further. In remaining patients, greater than 10 alpha EEG arousals/h (Spontaneous Arousals) along with flattening or plateau of inspiratory flow contour (by nasal cannula) was employed to diagnose UARS non-invasively. Epi-info software was used in statistical analysis.Results: Out of 25 patients with EDS, 60% (15) were diagnosed as OSA based on Apnea-Hypopnea Index (AHI) > 10/hr. Among 15 OSA patients,10 patients had severe (AHI >30); 2 had moderate (AHI 15-30) and 3 had mild OSAS (AHI 10-15). Only one patient was provisionally diagnosed as UARS based on nasal air flow graph and spontaneous arousals/hr >10.Conclusions: Upper airway resistance syndrome (UARS) is a distinct sleep disorder from obstructive sleep apnea syndrome (OSAS) with unique pathophysiology and it need be evaluated in all patients with unexplained arousals

Effects of the CPAP Treatment on the NON-REM Sleep Microstructures in Patients with Severe Apnea-Hypoapnea Syndrome

Sleep quality is affected in patients with sleep apnea- hypopnea syndrome (SAHS) with nocturnal and diurnal consequences. Most of these patients who are treated with positive airway pressure (CPAP) return to normal sleep patterns. We could consider good sleepers those patients who present more sleep spindles in stage II, and slower wave sleep as a good sign of better sleep quality. The objective in this research study was to compare the microstructure of stage II using the number of spindles and the increase of slow wave sleep before and after CPAP night titration. We developed a wavelet filter using a spline cubic function from a wavelet mother, which was appropriate to be used over electroencephalographic signal. By means of this filter in a multi-resolution mode, the spindles were detected from the increase of the IV band power; the sampling rate of the device determined the filter characteristics. The staging of polysomnographic studies was made by an expert according AASM (American Academy of Sleep Medicine) and then processed by the filter to get the index of sleep spindles before-and-after CPAP during stage II as well as the relationship between fast and slow powers from the EEG signal. An increase in the power of the slow waves vs. fast activity was observed in all the cases as a feature of better sleep. The neuroprotective effect described in previous research works regarding the density of the sleep spindles seems to be detected in patients improving their sleep quality after the correction of the apnea-hypopnea syndrome using CPAP.Fil: Smurra, Marcela. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos Dr. Enrique Tornú; ArgentinaFil: Blanco, Susana Alicia Ana. Universidad de Belgrano. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Eguiguren, Veronica. Gobierno de la Ciudad de Buenos Aires. Hospital General de Agudos Dr. Enrique Tornú; ArgentinaFil: Di Risio, Cecilia Diana. Universidad de Belgrano. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

APAP titration in patients with mild to moderate OSAS and periodic limb movement syndrome

(APAP) titration in a partially attended setting; 2) to verify whether APAP performance depends on the apneahypopnea and periodic limb movement indexes (PLMI). Methods. 65 CPAP naïve subjects with a sleep disorder of breathing and daytime sleepiness underwent a standard polysomnography (first night), APAP titration (second night, partially attended), and a standard polysomnography using continuous positive airway pressure (CPAP) at the effective pressure (Peff) established from the APAP titration (third night) in a sleep disorder laboratory in a 400-bed community hospital. We examined the apnea-hypopnea index (AHI), sleep stages, arousals induced by respiratory events (RESPa) and PLM (PLMa), and oxygen saturation during the first and third nights on CPAP at the Peff. Patients were divided into three groups according to their AHI and PLMI. Results. At the Peff defined using APAP on the third night, the mean AHI dropped from 29.6 ± 21.8 to 3.1 ± 3.4, and the RESPa index from 16.5 ± 16.2 to 1.7 ± 2.6. No differences emerged in sleep stages or spontaneous arousals (first vs third night). Overall, 92% of the patients met the standard for an acceptable outcome of positive pressure titration. Baseline AHI and PLMI did not affect the outcome of titration. Conclusions. In patients with mild to moderate OSAS and PLMS, APAP titration enables the optimal fixed pressure for CPAP home therapy to be determined in at least 90% of patients

Correlation between the Severity of Obstructive Sleep Apnea and Heart Rate Variability Indices

The risk of cardiovascular disease is known to be increased in obstructive sleep apnea syndrome (OSAS). Its mechanism can be explained by the observation that the sympathetic tone increases due to repetitive apneas accompanied by hypoxias and arousals during sleep. Heart rate variability (HRV) representing cardiac autonomic function is mediated by respiratory sinus arrhythmia, baroreflex-related fluctuation, and thermoregulation-related fluctuation. We evaluated the heart rate variability of OSAS patients during night to assess their relationship with the severity of the symptoms. We studied overnight polysomnographies of 59 male untreated OSAS patients with moderate to severe symptoms (mean age 45.4± 11.7 yr, apnea-hypopnea index [AHI]=43.2±23.4 events per hour, and AHI >15). Moderate (mean age 47.1±9.4 yr, AHI=15-30, n=22) and severe (mean age 44.5±12.9 yr, AHI >30, n=37) OSAS patients were compared for the indices derived from time and frequency domain analysis of HRV, AHI, oxygen desaturation event index (ODI), arousal index (ArI), and sleep parameters. As a result, the severe OSAS group showed higher mean powers of total frequency (TF) (p=0.012), very low frequency (VLF) (p= 0.038), and low frequency (LF) (p=0.002) than the moderate OSAS group. The LF/HF ratio (p=0.005) was higher in the severe group compared to that of the moderate group. On the time domain analysis, the HRV triangular index (p=0.026) of severe OSAS group was significantly higher. AHI was correlated best with the LF/HF ratio (rp=0.610, p<0.001) of all the HRV indices. According to the results, the frequency domain indices tended to reveal the difference between the groups better than time domain indices. Especially the LF/HF ratio was thought to be the most useful parameter to estimate the degree of AHI in OSAS patients

The relation between electrodermal activity in sleep, negative activity affect, and stress in patients referred for nocturnal polysomnography

The study of electrodermal activity (EDA) began over a century ago, and the phenomenon has been linked to many aspects of emotion, arousal and attention. A subset of studies has focused on the occurrence of EDA in sleep (EDAS). These investigations have led to definitive conclusions on when EDA is most likely to occur during the sleep cycle, i.e., slow-wave sleep. Studies have also shown that at least moderate stress tends to increase EDAS, but these studies have fallen short methodologically. The aims of the present study were: (a) to investigate the relation of negative affect and stress to EDAS, and to determine the extent to which these variables are predictive of EDAS; and (b) to explore the utility of EDAS as an index of sympathetic nervous system arousal and of sleep quality. Several additional hypotheses were also tested. Participants were 70 referrals to a local sleep disorders center. Subjects completed a demographic profile form and self-report measures of mood disturbance, worry and stress and underwent skin potential measurement during an overnight sleep study. Correlation and multiple regression analyses determined that weak relations exist between negative affect, worry and stress and EDAS, and that these variables are largely ineffective in predicting EDAS in a sleep-disordered population. Further, EDAS had no relation to self-reported sleep quality in this sample. Additional analyses found significant associations between apneic and periodic limb movement events and both central (EEG) and autonomic arousals (EDAS), and that a combination of both central and autonomic nervous system arousal variables might provide a better indicator of the amount of sleep disturbance present

EEG arousal prediction via hypoxemia indicator in patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea syndrome (OSAS) is a sleep breathing disorder characterized by recurrent airflow obstruction caused by a total or partial collapse of the upper airway. OSAS is a common affliction suffered by millions. The arousal index (ArI) is the best predictor of daytime somnolence for patients with OSAS, however, the polysomnography (PSG) examination in the sleep lab is expensive, time consuming and labor intensive. The objective of this study is to evaluate the ability and reliability of arousal prediction via the hypoxemia indicator in patients with OSAS. Patients with a diagnosis of OSAS by standard polysomnography were recruited from China Medical University Hospital Centre. There were 248 patients in the learning set and 255 patients in the validation set. The presence of OSAS was defined as an Apnea Hypopnea Index (AHI) >5/h. We used the hypoxemia indicator to predict ArI in patients with OSAS by linear regression and evaluated the prediction performance in different clinical characteristics subsets. The standard error of estimate of ArI prediction was 12.9 in the learning set. For predicting the severity of ArI, for ArI exceeding 15/h or 30/h, the sensitivity was 53.4% and 75.7%, respectively, with corresponding specificity of 96.6%, and 77.4%, respectively. We analyzed the hypoxemia indicator for predicting the severity of sleep fragmentation. The result demonstrated it ispossible to predict ArI via the hypoxemia indicator, especially in severepatients

Treatment of sleep apnea in chronic heart failure patients with auto-servo ventilation improves sleep fragmentation: a randomized controlled trial

Background: Impaired sleep efficiency is independently associated with worse prognosis in patients with chronic heart failure (CHF). Therefore, a test was conducted on whether auto-servo ventilation (ASV, biphasic positive airway pressure [BiPAP]-ASV, Philips Respironics) reduces sleep fragmentation and improves sleep efficiency in CHF patients with central sleep apnea (CSA) or obstructive sleep apnea (OSA). Methods: In this multicenter, randomized, parallel group trial, a study was conducted on 63 CHF patients (age 64 +/- 10 years; left ventricular ejection fraction 29 +/- 7%) with CSA or OSA (apnea-hypopnea Index, AHI 47 +/- 18/h; 46% CSA) referred to sleep laboratories of the four participating centers. Participants were randomized to either ASV (n = 32) or optimal medical treatment alone (control, n = 31). Results: Polysomnography (PSG) and actigraphy at home (home) with centralized blinded scoring were obtained at baseline and 12 weeks. ASV significantly reduced sleep fragmentation (total arousal indexpsc: -16.4 +/- 20.6 vs.-0.6 13.2/h, p = 0.001; sleep fragmentation index(home):-7.6 +/- 15.6 versus 4.3 +/- 13.9/h, p = 0.003, respectively) and significantly increased sleep efficiency assessed by actigraphy (SEhome) compared to controls (2.3 +/- 10.1 vs.-2.1 +/- 6.9%, p = 0.002). Effects of ASV on sleep fragmentation and efficiency were similar in patients suffering from OSA and CSA. Conclusions: At home, ASV treatment modestly improves sleep fragmentation as well as sleep efficiency in CHF patients having either CSA or OSA. (C) 2015 Elsevier B.V. All rights reserved

Resting state functional thalamic connectivity abnormalities in patients with post-stroke sleep apnoea: a pilot case-control study

OBJECTIVE: Sleep apnoea is common after stroke, and has adverse effects on the clinical outcome of affected cases. Its pathophysiological mechanisms are only partially known. Increases in brain connectivity after stroke might influence networks involved in arousal modulation and breathing control. The aim of this study was to investigate the resting state functional MRI thalamic hyper connectivity of stroke patients affected by sleep apnoea (SA) with respect to cases not affected, and to healthy controls (HC). PATIENTS AND METHODS: A series of stabilized strokes were submitted to 3T resting state functional MRI imaging and full polysomnography. The ventral-posterior-lateral thalamic nucleus was used as seed. RESULTS: At the between groups comparison analysis, in SA cases versus HC, the regions significantly hyper-connected with the seed were those encoding noxious threats (frontal eye field, somatosensory association, secondary visual cortices). Comparisons between SA cases versus those without SA, revealed in the former group significantly increased connectivity with regions modulating the response to stimuli independently to their potentiality of threat (prefrontal, primary and somatosensory association, superolateral and medial-inferior temporal, associative and secondary occipital ones). Further significantly functionally hyper connections were documented with regions involved also in the modulation of breathing during sleep (pons, midbrain, cerebellum, posterior cingulate cortices), and in the modulation of breathing response to chemical variations (anterior, posterior and para-hippocampal cingulate cortices). CONCLUSIONS: Our preliminary data support the presence of functional hyper connectivity in thalamic circuits modulating sensorial stimuli, in patients with post-stroke sleep apnoea, possibly influencing both their arousal ability and breathing modulation during sleep